It doesn't necessarily have anything to do with cities. An artist might appose areas of light and darkness in his paintings to increase the dramatic effect, for example.
I tried to quickly Google some sample sentences but the examples I found were misuses of the word ("he apposed the war" which should be "he opposed the war") or definitions of the word.
I haven't seen or heard it much as a verb. "Apposition", as a noun, is more common, in my experience. I believe mathematicians use the word "appose" in a very specific sense, but I can't remember what it is.